It is well recognized that oligosaccharides have a variety of biologically important roles either as free carbohydrates or as constituents of glycoconjugates. In plants free oligosaccharides play important roles in carbon fluxes within the cells and as a regulator. Oligosaccharides bonded to proteins also influence protein stability, folding, and biological functions of glycoproteins. Intercellular recognition by proteins may be affected by the structure and nature of oligosaccharides. Thus the characterization of complex oligosaccharides obtained from a variety of biological media has become of increased importance, involving many kinds of analytical techniques.
Unfortunately due to the restricted amount and complexity of samples obtained from biological media and the low proton affinity of oligosaccharides, there are many problems to be solved for the effective purification and the sensitive detection of oligosaccharides. In order to improve the sensitivity and the detectable mass range of oligosaccharides, derivatization methods such as reductive amination, designed to form a covalent bond with a variety of ligands containing nitrogen atoms, were introduced.
By the reductive amination method, the detection limit of derivatized oligosaccharides was improved greatly to fmol levels. But prior to analysis of the sample derivatized by this method, a purification procedure for the removal of excess reagents, such as sodium cyanoborohydride and the non-volatile organic ligand used, is necessary. This procedure sometimes is tedious and can be problematic especially in cases where restricted amounts of sample are available.
Therefore, for more convenient and low-level detection of oligosaccarides without pre-treatment of sample, the development of new derivatization methods for oligosaccharides is desirable.